1. Field of the Invention
The present invention relates generally to multi-band ZigBee transceivers for supporting IEEE 802.15.4 wireless communications and, more particularly, to a multi-band ZigBee transceiver for supporting IEEE 802.15.4 wireless communications, which includes an intelligent channel selection block, thus selecting a channel to minimize the influence of many interferers, and which includes a multi-mode modem, thus selectively and simultaneously supporting European/US/worldwide version ZigBee standards that support wireless sensor networks.
2. Description of the Related Art
Recently, with the rapid increase of wireless communications, demands for wireless sensor networks among a plurality of applications related to wireless networks have increased. It is recognized that ZigBee wireless communications based on network standards of Institute of Electrical and Electronic Engineers (IEEE) 802.15.4 having low power consumption and low data rate play an important part in Ubiquitous computing.
ZigBee wireless communications can be classified into European version standard using 860 MHz band, North American (US) standard using 920 MHz band, and worldwide version standard using 2.4 GHz Industrial, Scientific and Medical (ISM) band.
FIG. 1 is a block diagram of a conventional wireless communication transceiver. As shown in this drawing, the typical wireless communication transceiver is composed of a BaseBand (BB) modem 100 that performs modulation and demodulation using modulation and demodulation schemes defined by the physical layer specifications of each standard, a Radio Frequency (RF) front-end block (or RF/analog block) 105 that converts a digital modulated signal, output from the modem, into an RF modulated signal and converts an RF modulated signal, received from an antenna 110, into a digital modulated signal, and the antenna 110 that wirelessly transmits and receives the RF modulated signal.
In the transmission operation of the RF front-end block 105, a Digital-Analog Converter (DAC) 115 converts a signal, digitally modulated by the modem 100, into an analog modulated signal according to bit resolution corresponding to a selected standard, and a Direct Current (DC) component correction and Low-Pass Filter (LPF) unit 120 removes a DC offset from the analog modulated signal output from the DAC 115, and low-pass-filters the analog modulated signal to a bandwidth corresponding to a selected transmission standard.
Frequency up-converters 125 and 130 up-convert the In-phase (I) component of the BB analog modulated signal, output from the DC component correction and LPF unit 120, and the Quadrature (Q) component thereof into an RF band corresponding to the selected transmission standard, and output I and Q RF modulated signal components, respectively. The I and Q RF modulated signal components are combined together by an adder 135, and the output of the adder 135 is amplified by a power amplifier 140.
The RF modulated signal is output to the antenna 110 at transmission periods based on TDD through a transmission/reception switch 145. In this case, the RF modulated signal passes through a Band-Pass Filter (BPF) 150 to allow out-of-band spurious signals to be removed therefrom.
In the reception operation of the RF front-end block 105, the RF modulated signal, input from the antenna 110, is freed from out-of-band spurious signals by the BPF 150, and is input to the transmission/reception switch 145.
The transmission/reception switch 145 outputs the RF modulated signal, output from the power amplifier 140 of a transmission side, toward the antenna 110 through the BPF 150 at the intervals of transmission and reception, or inputs the RF modulated signal, received from the antenna 110 and passed through the BPF 150, to the Low Noise Amplifier 170 of a reception side.
The LNA 170 low-noise-amplifies an analog modulated signal (RF modulated signal) in an RF frequency band. The low-noise-amplified analog modulated signal is down-converted into BB modulated signals by frequency down-conversion mixers 175 and 180 with respect to the I and Q components thereof. A low-pass filter and programmable gain amplifier 185 low-pass-filters the down-converted BB band modulated signal to channel bandwidth corresponding to the transmission standard and performs BB amplification with respect to the I and Q components.
An Analog-Digital Converter (ADC) 190 converts the above-described BB signal into a digital modulated signal according to a bit resolution corresponding to the selected transmission standard, and outputs the digital modulated signal to the BB modem 100.
In regard to the generation of a carrier, a programmable divider 160 diminishes a local oscillation frequency generated by an oscillator 155, and a frequency synthesizer 165 generates a carrier frequency using a frequency output from the programmable divider 160.
The construction of the above-described conventional wireless communication transceiver supports only a single standard. In the single-standard-supporting transceiver, it is possible to design a multi-mode transceiver by combining together transceivers for supporting respective standards in parallel so as to support multiple modes. However, in this case, it is difficult to meet cost, size and power consumption requirements demanded by a variety of applications. That is, the method of merely integrating a plurality of single standard transceivers in a system causes an increase in implementation size attributable to the duplication of functional blocks and significant power consumption, so that it is not easy in terms of product competition to adopt the method. Therefore, the necessity of a scheme of supporting multiple modes using multiple bands through the use of a single wireless transceiver has increased.